The operability and reliability of semiconductor devices are typically tested after production. This process may result in cracking and even in delamination at the boundaries between the various materials of the semiconductor device due to increased temperatures. In particular, cracking between the circuit carrier and the plastic package compound is a problem.
Inadequate adhesion between a system carrier and the plastic package compound in semiconductor devices results in moisture collecting in the boundary layer between the system carrier and the plastic package compound. This moisture expands abruptly when the semiconductor device is heated from room temperature to temperatures of up to 260° C. in a very short time (e.g., during soldering onto a printed circuit board). The abrupt expansion in the moisture content results in cracks and/or fractures in the plastic package of the semiconductor device, often referred to as the “popcorn effect”.
To prevent this popcorn effect, moisture must be prevented from collecting in the boundary layer between the semiconductor device components and the plastic package compound. The collection of moisture can be reduced by improving the adhesion between the surfaces of the semiconductor device components and the surface of the plastic package compound. Various approaches are known for improving this adhesion.
U.S. Pat. No. 5,554,569 discloses a method for mechanically roughening the surface of a flat conductor frame. The roughened surface allows interlocking with the plastic package compound and hence better adhesion. However, this method is difficult and costly to perform.
It is also known to put an adhesion promoter on the system carrier prior to assembly. In U.S. Pat. No. 5,122,858, a polymer layer is put on a flat conductor frame.
German Patent Document No. DE 101 24 047 discloses an electronic device with semiconductor chips and system carriers, and also methods for producing same, where a metal system carrier has an electrodeposited adhesive layer comprising metal oxides, particularly of the metals zinc and chromium, to form a dendritic morphology. This device and the production method have the drawback that a dendritic morphology of this kind can be produced by electrodeposition exclusively on metal surfaces, which means that this adhesion promoter layer cannot be produced for semiconductor device components, such as system carriers made of ceramic or printed circuit board material, without prior coating with a shorting but metallically conductive layer.
There is also a need for improved reliability in the case of “green” devices, which need to meet the future requirements of environmental laws. In particular, the use of lead-free solder is desired. However, lead-free solder has the drawback that a higher soldering temperature of 260° C. is required. Consequently, cracking is a particular problem in the case of “green” devices.